I bought a couple of laser dot diodes off of the internet for a laser tag project, the three-volt, 2-wired 650nm kind. So I was worried about blowing it out and wasting a couple of weeks and a perfectly good $0.99, so I tried to do some research on hoe to hook 'em up to my Arduino. I could find NOTHING. Absolutely nothing. So I am going to help the tinkerers of Earth by making their lives more convenient.
Step 1: Editing the Program
Open arduino and go to files>examples>basics>blink and open it. Change LED_BUILTINto 12 every time it appears in the code. Take the negative wire and hook it up to the ground pin on your arduino. Now take the positive wire and hook it up to pin 12. Plug in the arduino and upload the newly-edited blink code. And there you go.